


On Your Side

by AbsinthexMind



Series: Oh brother where art thou [40]
Category: Harry Potter - J. K. Rowling
Genre: Brother-Sister Relationships, Brother/Sister Incest, Brotherly Love, Brothers, F/M, Incest, Secret Relationship, Sibling Incest, Supportive Sirius Black, secret is safe, what a good brother
Language: English
Status: Completed
Published: 2019-07-29
Updated: 2019-07-29
Packaged: 2020-07-11 21:50:36
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,596
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19935058
Author URL: https://archiveofourown.org/users/AbsinthexMind/pseuds/AbsinthexMind
Summary: Tumblr RequestNo matter what, Sirius would always be your big brother and be on your side.





	On Your Side

That was odd. 

“What are (y/n) and Regulus doing out so late?” Sirius ponders as he squints at the charmed map that James was helping him hold up. Sirius’ other hand was occupied with holding onto his wand, illuminating the unmoving names on the parchment: Regulus Black and (y/n) Black. 

“A lot of people would ask us the same thing. Leave them be Paddy. Or else you’ll turn into a mother hen.” James chuckles and nudges his partner in the side. “Plus they’re Slytherins. No offense but who knows what crazy things they’re doing.” 

He should’ve listened to James, but the protective brother side of him worried that his younger siblings would get in trouble if they were caught. 

Pressing his lips together briefly, Sirius makes up his mind. “Lets just check in on them really quick, yeah?” 

James shrugs. “Alright mate. If you’re really worried about them. I don’t know why you would though. From what you’ve told me they’ve already been brainwashed by your mum.” 

Mainly it was Regulus. (y/n) only followed suit because she wanted to stay near Regulus’ side. She had always been closer to him than she was to Sirius. She loved both of her brothers though, that was clear when she would smile warmly at Sirius or if their mother had locked him in his room for misbehaving she was the one to sneak meals to him. (y/n) was always sweet and loving to Sirius when she could be. Sirius’ soft spot lay primarily with her. He worried mainly for her as Regulus dragged her toward learning the dark arts. He had too much influence over her. 

Sirius at least had to try and protect her. Even if she was willing to follow Regulus in whatever path he took. 

To many, the halls of Hogwarts at night might have been eerie, but to James and Sirius it was their playground. They had spent many nights roaming the corridors, finding secret passageways, and perfecting their map. They walked with complete confidence, knowing the whole castle like it was the back of their hand. 

They hopped around on the moving staircases with ease as if it was some game that children played. 

“It’s gonna be this classroom up ahead.” Sirius whispers, leading the way while James carried around the invisibility cloak just in case there were any patrolling teachers. 

Creeping up on the aforementioned door, Sirius utters ‘alohamora’ to open the door a slight margin so that he could peer in. There was a distinct noise filling the silence. Soft kissing noises and the rustling of fabric as limbs moved restlessly. 

A soft gasp echoes out, drawing a curious James closer. The room was so dark that neither of them could make out much except the blocky figures of desks; upon which were two wreathing bodies. 

“Regulus.” A mewling, begging voice sighs out. 

Sirius would never mistake that voice for someone else’s. It was (y/n)’s. 

Oh. 

Sirius felt himself reel before growing numb, the ground underneath him shifting so that he felt off balance. By accident he backs up into James who stumbles a bit before catching himself. 

In a hushed tone, James stutters “What’s going on?” 

“Move!” Hisses Sirius in reply. He urgently pushes James in the direction they had come from. “Move, move!” 

That was (y/n) and Regulus. His younger sister and brother. And they were definitely making out.  
  
  
*  
  
  


“What’s wrong Reg?” Biting down on your crunchy toast, you notice your brother glaring in the direction of the Gryffindor table. 

Regulus’ handsome face is scrunched up as he tears his gaze away. “He’s staring again.” 

Cautiously you peer over to your older brother’s house. You had already known who Regulus meant. For the past couple of days both of you had caught Sirius staring at you and Regulus. You wanted to confront Sirius yourself to ask him what was going on but you never could find the right moment. The other Slytherins already glared at you whenever you merely said hello to Sirius. No matter what house he was in he was still your brother. You didn’t want to ostracize him like the rest of your family did. 

“Ah.” Regulus’ hand briefly brushes against your neck, pushing aside your (h/c) hair. A shiver ran all through your body. “You forgot to conceal this one, (y/n).” Over the chattering of students, no one would have been able to hear him. 

His knuckle gently presses down on the blossoming bruise on your neck. It tingled making your heart pick up pace. You must have missed that hickey due to your hair covering it up. 

You blush and rummage through your book bag for your wand. Pretending to scratch at your neck with it, you whisper a charm that would make it disappear; at least for a little while. 

“I hate when you hide them.” Regulus goes back to his breakfast but by now it’s merely a show since he lost his appetite. 

Rolling your eyes you reply “You know I have to. Otherwise everyone would ask where I got it from. I can’t be getting that kind of attention. 

Of course he knew. Still didn’t mean that he liked it. Like any guy, Regulus wanted to show off that you were his girl. That could never happen though. You were his sister. Even though incest was rampant in pureblood families it was discouraged that siblings take part in such relationships. Cousins were the ideal pairing since the blood was still slightly watered to prevent future children having deformities. 

Regulus tried to assure you many times that if the two of you confronted your parents that they would agree to allow the two of you to marry. You would still be keeping the bloodline pure. How could they oppose? 

It wasn’t a wise idea to show off your relationship at school. You knew among other wizarding families that they would consider it to be gross. You didn’t want people looking at you with disgust because you happened to be in love with your brother. Like you had planned to fall in love with him the whole time. No, things just happened. You had absolutely no control over the matter. 

Wanting to cheer him up, you put on your most charming smile and reach out to place your hand on top of his. Harmless, right? “Hey, we’re still on for tonight though, right?” 

That manages to make him smile and flip his palm up so that he now held onto your hand, fingers interlaced. “I wouldn’t miss it for the world (nickname).” 

You had to fight the urge to kiss him right there in front of everyone. 

You knew it wasn’t the perfect relationship, but you wouldn’t trade it for anything else.  
  
  
  
  


“You should have seen her face Reg!” Giggles escalated to a snorting fest making Regulus laugh. “Moustache out to here! And the pixies were poking their heads out like it was a magical forest!” 

There was always a shimmer in his eyes when he watched you laugh. Especially when you laughed so hard that you were reduced to snorting. He thought it was the cutest damn thing ever. 

That shimmer died as he halted. Students who were on their way to their respective classes walked around you and Regulus. 

You smile at your eldest brother who had stopped as well right in front of the two of you. “Sirius!” Smile faltering when you observe how awkward Sirius seemed standing there. 

He waited for the corridor to thin and empty out before speaking. At least he tried to at first. Sirius would open his mouth then shut it again to search for better words. After doing this a few times he gave up with an exasperated sigh and shoved a brown paper bag at you. 

When you wrap your arms around it you hear a clinking coming from within. You peer into the bag that was filled with various glittering vials and bottles. “Wh. . . What’s this?” Confused you look back up at Sirius. Regulus peered over your shoulder. 

“You guys are young. A. . . And you don’t need a baby ruining your lives right now.” Sirius is blushing furiously as he continues. “If you are going to be together at least be safe about it, okay?” 

It dawned on you fairly quickly what Sirius was saying. He knew about you and Regulus. And he was giving you contraceptive potions. 

You feel your cheeks burst into flames. “Oh Merlin!” Burying your face into the bag, Regulus chuckles. 

“Really? You don’t find it gross that your siblings are in an intimate relationship together?” 

“It’s. . . a little unusual but no. You guys aren’t gross. You’re my little siblings. I just want you to be safe. And I want you to take care of her Reg.” Blush subsiding, Sirius’ dark eyes are trained on his younger brother. 

Shooting a worried glance at Regulus, his face softens incredibly. “Of course I will. Thank you Sirius.” 

Sirius grins, playfulness returning. “Don’t mention it.” 

That was the first time in years that you had seen Regulus act friendly toward Sirius. You can’t help but smile at your brothers. Happy that Regulus saw how Sirius was on your side no matter what. 

“Well then, shall we skip class and try these out (y/n)?” Regulus turns to ask you. 

The blush returns to both you and Sirius’ faces. 

“HEY! Don’t say that in front of me!” Sirius complains. “I support you guys but I’m definitely not ready to hear that kind of stuff!!”


End file.
